On Wed, 28 Aug 2013 13:22:57 +0800
Cong Wang [off-list ref] wrote:

+#if IS_ENABLED(CONFIG_IPV6)
+static int neigh_reduce(struct net_device *dev, struct sk_buff *skb)
+{
+	struct vxlan_dev *vxlan = netdev_priv(dev);
+	struct neighbour *n;
+	union vxlan_addr ipa;
+	const struct ipv6hdr *iphdr;
+	const struct in6_addr *saddr, *daddr;
+	struct nd_msg *msg;
+	struct inet6_dev *in6_dev = NULL;
+
+	WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());

You may have needed warn during debugging, but you should be able
to audit all the codepaths (this is a static function) to be sure
that this code is correct (ie rcu lock always held).